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The Prusten Project has gained a large following over the past few years as word of our research and goal of helping save wild tigers as spread. But, how many truly understand the scientific aspects of our work? I hope through this blog post to explain a little more about the fine details of our organization and to help clarify the work we currently have ongoing in zoos across the United States.

There are very few, truly wild places left on our planet. As human populations continue to expand, more landscapes become encroached by our ever-growing society. Wild animals find their habitats shrinking and resources becoming ever more difficult to find. These fragmented human-dominated landscapes are also leading to an increase in human-wildlife conflict. The result is often disastrous for wild animal populations, especially those already classified as endangered, like the tiger, whose populations we are still struggling to understand and conserve. Since the early 1990s, tiger populations of all subspecies have plummeted by over 50% throughout their shrunken ranges currently only occupying 7% of their historic range (Seidensticker et al. 2001). Primarily responsible for this rapid decline is the growing illegal wildlife trade in various body parts from this species sold as health tonics and economic charms (Dinerstein et al. 2007). Habitat degradation and the increasing rate of prey depletion are also to blame alongside an increase in deaths related to conflict areas.

Assessing the population status of tiger populations requires a reliable method for measuring patterns of habitat use and overall abundance within range-land countries. Methods that have been used to study the distribution and patterns of habitat use by tigers include camera traps, radio-tracking, scat collection, as well as paw-print counts. These outdated tracking methods may cause more harm than good due to habitat invasion and disturbance and low efficiency (Karanth et al. 2003). Automatic cameras triggered by animal movement (a.k.a camera-traps) can provide more accurate information about tiger density, but here too there are inherent problems (e.g. tigers frequently cross a trap’s path without a sufficient photo taken).

Recently, the use of acoustic recorders has become increasingly common in studies related to population densities and habitat use of mammals, birds, and amphibians (Measey et al., 2017; Russo et al., 2017). Recordings of African forest elephants in central Africa have been able to not only the mechanisms of communication but also estimate population size, quantify threats, and assess the efficacy of conservation strategies (Wrege et al., 2017). Identification of individual animals by vocalizations has been shown plausible within the field of primate research (Chapman and Weary 1990; Lillehei and Snowdon 1978). In addition, Spotted Hyena vocalization studies have revealed sex discrimination possibility (Theis et al. 2007).

Acoustic monitoring holds promise of more efficient census efforts. Monitoring such as this is an obvious fit for describing tiger populations which inhabit dense forests, where visual observation is difficult or near impossible. It is also ideal for species which share the habitats of the tiger that are sensitive to disturbance, since an area can be monitored for months without visiting the site. In addition, acoustic monitoring could be less labor intensive than many other animal-counting methods while continuing to retain accuracy as shown by previous studies. It also opens up the opportunity to create an early alert system utilizing detected sound. Such a system could help mitigate human-tiger conflict by providing a warning to people about the anticipated arrival of tigers in human habitation in addition to being used to improve census.

The objectives of our study are to record tigers within controlled, ex-situ conditions to determine individualistic vocal characteristics. After being identified and annotated, the vocalization characteristics will be used to create a sensor system for use as an early warning system and an acoustic monitoring network for deployment in central India. The project will include collaborators from the bioacoustics organization called Sensing Clues which creates early warning & fast-response technologies for wildlife.

Tiger vocalization collection are currently occuring Association of Zoo and Aquarium (AZA) accredited facilities throughout the United States. Such facilities keep detailed records regarding the subspecies genetics of individuals so we are able to identify with certainty which particular subspecies an individual tiger belongs to. AZA-accredited facilities also institute standardized husbandry protocols at their facilities helping us ensure each tiger in the study is cared for in the same manner.

Recording sessions occur 24 hours a day using the Songmeter SM4 Platform in 16-bit full-spectrum uncompressed .WAV format. The recorders will either be mailed or hand-delivered to participating facilities. The facilities will also be provided with a document outlining the project goals as well as a tutorial on how to operate the recorder once it has arrived. One subject (individual tiger) will be the focus of a recording session which will consist of three nights. Each tiger will go through two rounds of recording resulting in a total of six recorded nights. Targeted vocalizations include prusten (chuffing), subroars, and long-distance calls which range from close-contact vocalization to communication over many kilometers. Furthermore, daily weather conditions (e.g. barometric pressure, cloud cover, humidity, temperature, precipitation) will be recorded to analyze any climatic effects. This data will be recorded from local weather stations.